Production of sodium



Filed Oct. 18, 1955 du mm2 INVENTOR. Rog C. K/-

United States .Patent-"O" -ical Company, Midland, Mich., a corporation of Delaware Application October 18, l1955, Serial No. 541,274 s Cia'i'ms. (SCi. '7s- 36) This invention relates to the production of sodium and, more particularly, to 'an impro'd process' Vfor producing sodiu'm by rnean's of a cyclical, thermal method.

A number of thermal processes for producing sodium have beenvkno'wn heretofore, but each proved to be un- 'economical because of the low yields `which were obtained. An improved thermal process has been disclosed andclaimed in U. S. Patent No; 2-,39l,7258, patented Dcce'mber 25, 1945, on an -application f ilcd in the naines of Thomas H. McConica III, Arthur A. MacPhail y'and the applicant as co-inventors. In brief, this patented process comprises, as one example, charging sodium carbonate and carbon to a high temperature reactor in which the carbon reduces the sodium carbonate to obtain sodium vapor and carbon monoxide. These gases are then passed through 4a condenser in which they 'are rapidly chilled by intimate contact with molten lead -to condense the sodium vapor to molten sodium vand thus separate it from the carbon monoxide. l

While this patented process' represents a marked improvement over the prior art, still some dross is formed upon condensation of 'the sodium vapor. Such dross formation is inherent in any high teiperaturethie'rmal production of sodium, since the sodium vapor and carbon monoxide will react to a limited extent (depending upon the rapidity of cooling) when they pass from the 'high reaction temperatures through the lower Vtemperature ranges during condensation. The dross may be readily separated from Athe molten sodium by adding thereto sodium hydroxide as a flux, but the amount of sodium hydroxide required for this fluxing operation is approximately equail to the total weight of sodium recovered. Consequently, a large percentage of the sodium values added as raw materials is found in this ilux. Separation of the components of the ux is not economically'feasible. Due to the large sodium hydroxide content, this flux cannot be recycled through the high temperature reactor. At temperatures of l200 C., at which this reactor 'opcrates, sodium hydroxide has a very high vapor pressure and reacts readily with the graphite 'lining employed in such reactors. Thus, the sodium values in the flux are lost, and the eliiciency of the overallprocess 'suffers cc`ording1y.

It is an object of this invention, therefore, to provide a cyclical process for producing -'sodium wherein substantially all of the sodium values. are recovered from the dross obtained in'the high temperature thermal production cf sodium. Other Yobjects of this invention iwill become apparent from the following detailed description thereof.

In practicing the process ofthe present invention, sodium carbonate is reduced with carbon in a high tempeinture reactor in the --man'ner described above in connection with Patent No. 2,391,728. A charge of sodium carbonate 'and some suitable formof carbon such as coke, is fed to a reactor wherein ythe pressure and temperature are such as to produce sodium yapor and caronfmonoxide. The sodium vapor `and carbon `monoxide are 2,774,663 .Patented 18V, `195,6

rapidly cooled in a condenser through intimate contact with a condensing rncdiuin such as molten sodium, molten lead or ures thereof.V Some dross is inevitably formed du 'g this V'condensation operation and vis separated .from 'the molten sodium by fluxing with sodium hydroxide. l

In carrying out the Icyclical process of the lpresent -in vention, this ilux, which is in the hot huid state and contains the dross formed in theghigh 'tterripei'ature reactor, is lheated along rwith added sodium hydroxide and carbon in a low temperature reactor to produce sodium vapor, hydrogen gas and residual sodium carbonate. The Vsodium vapor is separated from thc hydrogen by passing it through a condenser such as a molten pool of and the residual sodium carbonate is removed from ythe low temperature reactor `and recycled to the high ternperature reactor to complete thecycl'e.

This process utilizes 'by-product waste from the high temperature thermal reaction in a -second reaction yto perform the 'twofold function of recovering the sodium values therefrom 4a-nd to regenerate starting material for the hilgh temperature reaction. Consequently, the present invention still Vfurther improves the efficiency 'of the high temperature 1reduction of sodium carbonate. Furthermore, since the ksodium values in the dross are almost entirely recovered, economical modifications "of the sodiumV carbonate reduction process which previously could not be considered because of increased Adross formation, `can 4now be made. For example, substitution of a sodiumquench for a lead quench, with the accompanying elimination of distillation operations, is economically feasible "in spite of substantial increases in the amount of dross formed.

In describing the present invention in detail reference is made to the accompanying drawing which comprises a flow sheet outlining the Aone example of the subject process. A charge is made up for reactor No. 1 by combining pitch, coke, and lsodiui' carbonate, inthe form of briquettes.

While coke is a preferred `'source of carb'on Some pitch is desired for use as a binder in ythe briquetting operation. By combining ythe carbon land .sodium carbonate 'in intimate mixture in briquettes, `the sodium carbonate reacts withthis added carbon rather thanwi'th 'the graphite `liner in the reactor. Also, briquetting provides the added .function of reducing'the fines which lcontribute materially to the amount of dross obtained in the condenser. vscrew conveyor may be used to feed vllthe'se briquettes yto reactor No. '1 which, in this .specific example, jis an electric arc furnace having awgraphite lining. This `reactor is maintained at a temperature between 9'0'05" and i500 C., preferably at least 1200 C. The pressure within the 'reactor must exceed that in the condenser in order 'to tforce thcsodium vapor from the reactor into the'co'n'd'enser. mately 0.5 atmosphere is preferred.

The sodium v'por and carbon monoxide gas produced infreactor No. v1, 'are forced `by the pressure within the lreactor out through `v'an oriiicejinto the condenser, which fis 'rnsintained at anni ximo-'ery 3001n C. and Vat a 10W "pressure yof about one inch 'of mercury. Although the "charg -rbetto'n'ie interinxed 'with the finolten 'so'diu'rn to .prod-'ucc dross. 'This dross passs withlthem'olten sodium A lreactor pressure of approxiinto a reservoir wherelake sodium hydroxide is added to flux the dross from the sodium. The temperature of the sodium in the reservoir must be within the range of 290 C. to 500 C. in order to prevent reactionwith the sodium hydroxide. The freed sodium is then drawn off at a'predetermined rate, part of it being recirculated through a heat exchanger for use as a quenching medium and the remainder being separated as the end product. The hot uid ux, which consists principally of sodium hydroxide and sodium carbonate, along with some unreacted carbon and occluded sodium, is drawn ofi from the bottom of the reservoir.

Up to this point, the ow sheet process is quite similar to the process disclosed in Patent No. 2,391,728.

Theprimary difference is that the patent discloses the use of a lead quench rather than a sodium quench, which requires a still for recovering hte molten sodium from the molten lead. Of course, the lead quench can be used actor No. 2 along with added sodium hydroxide and coke.

A major advantage of the present invention resides in using this ux while still in thehot fluid state, since the flux is then free from Water and is at a temperature such that the heat requirements in the low temperature reactor are minimized. If the flux is allowed to cool and "harden, the large sodium hydroxide content would cause it to take on additional water, which would have to be removed by an additional heating step before it could be introduced into reactor No. 2. Also, the hardened ux would have to be ground to a size which could be conveniently handled. Elimination of these added steps greatly enhances the commercial feasibility of the process.

The second reactor is maintained at a pressure of approximately one atmosphere and at temperatures ranging from 700 to 900 C., although SOO-850 C. is preferred. Because of the relatively low temperatures involved, reactor No. 2 is preferably gas-fired. Upon reaction, sodium vapor, hydrogen, and residual sodium carbonate are produced. The sodium vapor and hydrogen gas are forced by the pressure within the reactor No. 2 into a condenser which is maintained at approximately 100 C. and at a pressure up to one atmosphere. This condenser may be just a pool of molten sodium through which the gases are bubbled. A heat exchanger can be used to cool the molten sodium, although heat losses may of themselves be suicient to maintain a constant temperature. The hydrogen does not condense in the condenser, of course, and is removed through a suitable vent. The sodium vapor does condense and is collected as the end product. The residual carbonateleft in the low temperature reactor No. 2 is not pure, and contains some unreacted carbon and sodium hydroxide. Still, it is adequate for use in the high temperature reactor and is removed from reactor No. 2 and combined with added coke and pitch to prepare thecharge for reactor No. l. In this manner, the cycle of the process is completed.

To better understand the significance of the applicants invention, reference is made to a material balance of the process outlined in the accompanying flowsheet. As

an example, two pounds of sodium carbonate and 0.45 pound of carbon (in the form of coke and pitch) fed to reactor No. 1 and treatedwith 0.70 pound of sodium hydroxide in the reservoir, as above described, produces 1.18 pounds carbon monoxide, ,0.70 pound sodium, and 1.27 pounds of flux. When this 1.27 pounds of ux lis combined with 1.0 pound of sodium hydroxide and 0.05 pound' of carbon (in the form of coke) in reactor No. 2, it produces 0.4 pund of hydrogen, 0.28 pound of sodium, and 2.0 pounds of sodium carbonate. All that need be added to this cyclical operation to produce molten sodium is carbon and sodium hydroxide, which is normally cheaper than sodium carbonate. Neither of these reactions, by itself represents an efficient means for recovering sodium values from the charged materials, but the cyclical process comprising the present invention effects more than a percent recovery of these sodium values.

It will be obvious to those skilled in the art that numerous variations in the process steps above set forth may be made without departing from the scope of the present invention. For example, the charge may be introduced into either reactor in a variety of ways, and any form will be satisfactory as long as intimate mixing of the charge ingredients is obtained and the fines are reduced to a minimum. Temperature and pressure variations in the reactors and in the condensers are interrelated and may be varied in a manner well known to those skilled in the art. Operational details, such as protective atmospheres, heat exchangers, etc. have not been extensively described since they form no part of vthe present invention, and their operation is familiar to those skilled in this art.

I claim:

A1. In a process for producing sodium which comprises reducing sodium carbonate with carbon in a high temper- Y ature reactor to produce sodium vapor and carbon moncomprises the steps of heating said ilux in a low tempera- -ture reactor along with added sodium hydroxide and carbon to produce sodium vapor, hydrogen and residual sodium carbonate, separating said sodium carbonate from the sodium vapor and hydrogen, and feeding said sodium' carbonate and added carbon into the abovementioned high temperature reactor to complete a cyclical process for making sodium.

2. In a process for producing sodium comprising reacting sodium carbonate with carbon in a high temperature reactor to produce sodium vapor and carbon monoxide, condensing the sodium vapor to produce a mixture of molten sodium and a dross consisting principally of sodiumcarbonate and carbon, fluxing the dross from the molten sodium by adding sodium hydroxide to said mixture and separating the molten sodium from the hot fluid ux, the improvement of converting this process to a cyclical operation which comprises the steps of reacting the hot fluid ux in a low temperature reactor along with added sodium hydroxide and carbon to produce sodium vapor, hydrogen, and residual sodium carbonate, separating the residual sodium carbonate from the sodium vapor and hydrogen, and feeding said residual sodium carbonate along with added carbon to the aforesaid high temperature reactor to produce more sodium vapor and dross and thus complete the cycle.

3. In a process for producing sodium comprising reacting sodium carbonate With carbon in a high temperature reactor to produce sodium vapor and carbon monoxide, condensing the sodium vapor with a molten sodium quench to produce a mixture of molten sodium and substantial amounts of dross consisting principally of sodium carbonate, carbon and occluded sodium, fluxng the dross from the molten sodium by adding sodium hydroxide to said mixture and separating the molten sodiumY from the flux, the improvement of converting this process to a cyclical operation which comprises the f steps of reacting the flux while still in a hot uid state in a low temperature reactor along with added sodium hydroxide and carbon to produce sodium vapor, hydrogen, and residual sodium carbonate, separating the residual sodium carbonate from the sodium vapor and hydrogen, and feeding said residual sodium carbonate along with added carbon to the aforesaid high temperature reactor to produce more sodium vapor and dross and thus complete the cycle.

4. In a process for making sodium comprising reacting sodium carbonate with carbon in a high temperature reactor to produce sodium vapor and carbon monoxide, condensing the sodium vapor to produce a mixture of molten sodium and a dross consisting principally of sodium carbonate and carbon, fluxing the dross from the molten sodium by adding sodium hydroxide to said mixture and separating the molten sodium from the llux, the improvement of converting this process to a cyclical operation which comprises the steps of reacting the hot flux while still in the hot fluid state in a low temperature reactor along with added sodium hydroxide and carbon to produce sodium vapor, hydrogen, and residual sodium carbonate, separating the resiual sodium carbonate from the sodium vapor and hydrogen, and feeding said residual sodium carbonate along with added carbon to the aforesaid high temperature reactor to produce more sodium vapor and dross and thus complete the cycle, the amount of sodium hydroxide and carbon reacted in said low temperature reactor being such that a predetermined amount of residual sodium carbonate is continuously produced and supplied to the high temperature reactor.

5. In a process for making sodium comprising reacting sodium carbonate with carbon in a high temperature reactor maintained at a temperature of at least 1200 C. and not more than 1500 C. to produce sodium vapor and carbon monoxide, condensing the sodium vapor with molten sodium to produce a mixture of molten sodium at temperatures between 290 C. and 500 C. and a substantial amount of dross consisting principally of sodium carbonate, carbon, and occluded sodium, fluxing the dross from the molten sodium by adding sodium hydroxide to said mixture and separating the molten sodium from the hot uid flux, the improvement of converting this process to a cyclical operation which comprises the steps of reacting the flux while still hot and fluid in a low temperature reactor at a temperature ranging from 700 to 900 C. along with added sodium hydroxide and carbon to produce sodium vapor, hydrogen, and residual sodium carbonate, separating the residual sodium carbonate from the sodium vapor and hydrogen, and feeding said residual sodium carbonate along with added carbon to the aforesaid high temperature reactor to produce more sodium vapor and dross and thus complete the cycle, the amount of sodium hydroxide and carbon reacted in said low temperature reactor being such that the residual sodium carbonate is continuously produced at a predetermined rate and supplied to the high temperature reactor.

References Cited in the le of this patent UNITED STATES PATENTS 2,391,728 McConica et al. Dec.v 2S, 1945 

1. IN A PROCESS FOR PRODUCING SODIUM WHICH COMPRISES REDUCING SODIUM CARBONATE WITH CARBON IN A HIGH TEMPERATURE REACTOR TO PRODUCE SODIUM VAPOR AND CARBON MONOXIDE, CONDENSING THE SODIUM VAPOR TO PRODUCE A MIXTURE OF MOLTEN SODIUM AND A DROSS CONSISTING PRINCIPALLY OF SODIUM CARBONATE AND CARBON, FLUXING THE DROSS FROM THE MOLTEN SODIUM WITH SODIUM HYDROXIDE AND SEPARATING THE FLUX FROM SAID MOLTEN SODIUM, THE IMPROVEMENT WHICH COMPRISES THE STEPS OF HEATING SAID FLUX IN A LOW TEMRPERATURE REACTOR ALONG WITH ADDED SODIUM HYDROXIDE AND CARBON TO PRODUCE SODIUM VAPOR, HYDROGEN AND RESIDUAL SODIUM CARBONATE, SEPARATING SAID SODIUM CARBONATE FROM THE SODIUM VAPOR AND HYDROGEN, AND FEEDING SAID SODIUM CARBONATE AND ADDED CARBON INTO THE ABOVE MENTIONED HIGH TEMPERATURE REACTOR TO COMPLETE A CYCLICAL PROCESS FOR MAKING SODIUM. 